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Tuesday, March 11, 2008

Slit lamp examination of eye

067. A patient had seven irregular hyperpigmented macules on the trunk and multiple small hyperpigmented macules in the axillae and groins since early childhood. There were no other skin lesions. Which is the most likely investigation to support the diagnosis?

1. Slit lamp examination of eye

2. Measurement of intraocular tension

3. Examination of fundus

4. Retinal artery angiography

Answer

1. Slit lamp examination of eye

Reference

Harrison 16th Edition Page 2457

Quality

Thinker

Status

New

Discussion

It is easy to arrive at an diagnosis. Axillary hyperpigmentations point to Neurofibromatosis. To confirm the diagnosis, we have to look for the Lisch nodules.

Explanation

1. Slit lamp examination of eye is done to diagnose Lisch nodules of Iris

2. Measurement of intraocular tension is also needed in Neurofibromatosis to rule out Congenital Glaucoma (often associated with the disease) but is not the most likely investigation to support the diagnosis

3. Examination of fundus is also done, but not for supporting the diagnosis

4. Retinal artery angiography will not help in supporting the diagnosis

Comments

Ocular manifestations of neurofibromatosis include

  1. Plexiform tumours of lids with Ptosis
  2. Thickened corneal nerves
  3. Pulsating proptosis (due to transmitted cerebral pulsations through the defects in the orbital walls)
  4. Glioma of optic nerve
  5. Congenital Glaucoma

Tips

Mutation of the NF1 gene on chromosome 17 causes von Recklinghausen's disease. The NF1 gene is a tumor suppressor gene; it encodes a protein, neurofibromin, which modulates signal transduction through the ras GTPase pathway. Patients with NF1 are at increased risk of developing nervous system neoplasms, including plexiform neurofibromas, optic gliomas, ependymomas, meningiomas, astrocytomas, and pheochromocytomas. Neurofibromas may undergo secondary malignant degeneration and become sarcomas.

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